Generally speaking, under water optical fiber cables comprise: a core including the optical fibers which are themselves either placed in tubes of plastics material filled with viscous material or else in helical grooves around a metal or plastic core member; a protective arch of steel wires wound helically around the core; a longitudinally welded tube of ductile metal (e.g. aluminum or copper) swaged down on the steel wires; and an insulating sheath of thermoplastics material such as polyethylene.
It is difficult to interconnect the ends of cables made in this manner, since all the following need to be achieved at once by the junction:
the optical fibers of the cables need to be connected end to end (usually by welding), and enough slack optical fiber must be left to avoid breakage in the event of traction being applied to the cable;
the structural protective arches of steel wires on the two ends must be mechanically joined with sufficient strength to withstand the traction to which the cable is subjected during handling; and
the junction must be watertight, even against the pressures to be found at the bottoms of the oceans.
One prior proposal for a junction to meet the above requirements rationally and rapidly when there are two cable ends to be joined uses an inner optical fiber supporting member which is free to move axially and to rotate. This can lead to the fibers being broken in the event of operator clumsiness.
Preferred embodiments of the present invention avoid this drawback and provide a junction which is simple to use and which is: mechanically strong; watertight by means of a filling of water repelling material; and well insulated electrically.